1. Field of the Invention
The invention relates to a method for producing the rotor winding of an electric machine and to an electric machine having a rotor winding produced by this method.
2. Description of the Prior Art
From German Patent DE 197 57 279 C1, it is known, in a four-pole electric motor, to use a commutator rotor with 12 commutator laminations and 12 coils connected to them, in order to attain low torque waviness and good commutation. The laminations that are diametrically opposed to one another are connected to one another via contact bridges, in order to make the current supply to the rotor symmetrical and to assure it with only one pair of brushes. In such machines, the rotor current is not distributed to two coil lanes, but instead, because of the contact bridges, to four coil lanes, with the disadvantage that per coil lane, only half as many coils are connected in series. Thus the commutator voltage at the coils is increased accordingly. This causes greater wear of the carbon brushes on the commutator and thus a correspondingly limited service life or durability of the motor. The coils of the rotor are furthermore wound over three pole teeth each, so that their winding heads intersect at the face ends of the rotor. This causes greater cantilevering of the winding heads and leads to long winding head connections of the coils, which are expensive in terms of material and also cause high heat losses.
From U.S. Pat. No. 4,532,449, a four-pole electric machine with a commutator rotor is also known, in which the number of rotor coils is only half as great as the number of commutator laminations. In it, five coils are supplied from one brush pair via 10 laminations. The coils are continuously wound as single-tooth windings, with a skip each time of one pole tooth from one coil to the next. The beginning and end of the coils are each contacted with laminations between which one lamination remains unoccupied. For supplying current to the coils via contact bridges, these unoccupied laminations are connected to the laminations diametrically opposite them, and these diametrically opposite laminations are connected to the coils. This embodiment has the disadvantage that because of an increased lamination voltage, with five coils instead of twelve, an increased brush fire occurs, which impairs the service life of the commutator and hence also the durability of the machine.
With the present embodiment, the object is, in electric machines with single-tooth coils and high numbers of poles, to improve the commutation and thus the service life of the machine.